I wanted to ask why those 2 instructions should be privileged
Unless I miss something, I can see no reason for that.
The [only] purpose of those 2 instructions is to save power.
They don't do anything that can have security consequences,
and have no effect on the architectural state of the processor, whatsoever.
Disallowing them for ring3 code only means that certain [spinlock] algorithms
that run in user space can not be as power-efficient as in ring0.
But isn't it in intel's best interest their processors to be as power-efficient as possible in all situations?